The invention relates to a method of giving preserved and non-preserved biological material endurance strength while retaining its natural size, consistency, dissecting capacity, plasticity, flexibility as well as internal and external structure.
For teaching and demonstration purposes as well as for museum archiving, particularly in anatomy, pathology and biology and their fringe areas, either so-called moist specimens or artificial models are used. Moist specimens have the disadvantage that they always have to be kept in preserving liquid and can only be removed briefly from this liquid for demonstration purposes. Artificial models are imitations of natural specimens and have the defects of inadequate fidelity of imitation, unnatural consistency, lack of flexibility and absence of dissecting capacity. For the production of natural demonstrated, there have hitherto also been the following possibilities:
1. The storage of the materials in preserving liquids in glass vessels, so-called wet specimens, PA0 2. the drying of the specimens, PA0 3. the freeze-drying of the specimens, PA0 4. the paraffining of dried or freeze-dried specimens, PA0 5. the embedding of plastics-impregnated objects in transparent blocks of plastics material, PA0 6. preserving sections of biological objects by means of a mounting medium between 2 glass supports or between foils, PA0 7. encasing specimens in plastics materials, PA0 8. the methods of giving specimens endurance strength by impregnation of the objects either directly or indirectly via intermedia by means of synthetic resins. PA0 1. extremely sensitive to external mechanical effects and PA0 2. the consistency of the tissue is altered considerably by the freeze-drying in the sense of hardening of the tissue.
The methods given above are as follows:
Method 1
Wet specimens are stored in a preserving liquid in glass containers. The preserving liquid must be renewed at regular intervals and the specimen is mechanically secured inside the glass vessel for demonstration purposes. With this kind of storage of demonstration material there is the disadvantage that the specimens can only be observed from outside and cannot be handled and manipulated. Superficial structures and structures in depth appear distorted as a result of the media diffracting differently. In addition, the specimens lose their natural colouring.
Method 2
The drying of biological specimens can only be carried out with small objects because a shrinkage of the material occurs as a result of the drying. The specimens thus produced also have the disadvantage that they can very easily be damaged by mechanical effects.
Method 3
It is true that freeze-dried biological specimens do not shrink, in contrast to dried specimens, and retain their shape, but they are
Method 4
Paraffin-impregnated specimens do not permit a clear detailed representation of the surface because paraffin is not transparent. In addition, such specimens are very liable to break and can only be kept clean with great expense.
Method 5
Specimens embedded in plastics material correspond in form to the wet specimens described under Method 1 but have the advantage in comparison with these that blocks of plastics material are more secure against breakage and the specimen is insensitive to external influences and a result of the embedding in the plastics material.
Method 6
Sections of specimens which are introduced between glass plates or foils have the disadvantage of a great risk of breakage and little flexibility.
Method 7
According to U.S. Pat. No. 2,698,809 there is disclosed a method for the external embedding of biological materials wherein the specimens are encased in plastics material while retaining satisfactory colour. With this method of treatment, the embedding agent does not penetrate into the specimen (Lit. Science Vol. 54,49-50, 1941). As a result of the hardening, objects thus treated are stiffened in their consistency, lose their plasticity and subsequently can no longer be dissected.
Method 8
The methods disclosed in German Patent specification No. 27 10147,9-41 for the permanent preservation of specimens of biological objects liable to decay and methods of producing them are suitable for demonstrating their exposed surfaces. The specimens can be felt and also observed through a magnifying glass. They have the disadvantage, however, that after the production of the specimen, dissecting that is to say a further systematic analysis of the specimen, is not possible, the consistency of the specimen no longer corresponds to its original one, the plasticity and flexibility of the tissue have altered considerably from its original state and the methods of production through intermedia or other solvents and the embedding in plastics materials are very time-consuming, expensive and suffer from a factor of uncertainty in the uniform production of specimens caused by the different hardening of plastics materials as a result of minor alternations in the amounts of synthetic resin components.
All the above methods of giving biological objects endurance strength suffer from drawbacks, because they lead to an alteration in the consistency as a result of homogenization of the tissues through the embedding agent combined with a more or less severe loss of plasticity and flexibility. In addition, a subsequent dissecting of the biological specimens thus treated is no longer possible. Furthermore, the methods of production are technically very extravagant and very expensive through the use of special chemicals for the impregnation and embedding.